1. Field of the Invention
This invention relates to the production of citric acid esterified partial fatty acid glycerides.
2. Description of the Prior Art
The presently known esters of citric acid with partial fatty acid glycerides are used primarily in the food industry. Generally, they serve to stabilize fatty emulsions and to act as synergistic agents for antioxidants which are used in fatty or fat type products.
A number of methods are known for production of these esters. Thus, for example, in German Patent Auslegeschrift DT-AS 1,278,423, the manufacture of the esters is carried out by the direct reaction of the partial fatty acid glyceride with citric acid. However, this process has considerable disadvantages and relatively limited application.
Thus, for example, only one mol of citric acid can react with one mol of the fatty acid monoglyceride. If an attempt is made to increase the molar reaction of the citric acid, the participation of the citric acid is decreased and it precipitates as a product of the reaction. Moreover, if an attempt is made to force the reaction to completion by increasing the temperature, the citric acid is decomposed in an uncontrollable manner. Also, the hydrophilic properties of the reaction product are lowered and as a result of the formation of other by-products, the resulting mixture is often physiologically unsafe.
Another known process is the reaction of citric acid with acetic acid anhydride to form an acetyl compound and a citric acid anhydride and then to esterify the anhydride with a partial fatty acid ester. However, with this reaction, the pure citric acid ester of the partial monoglyceride is not obtained. Rather, products are obtained in which the hydroxyl group of the citric acid is acetylized.
Consequently, upon storage and use of these reaction products, the acetic acid splits off and detrimentally affects the smell and taste of the food to which the reaction products have been added.